5-aza-2′-deoxycitidine (Decitabine) is an analogue of the natural nucleoside 2′-deoxycytidine and is shown in Figure 1.

Decitabine is believed to exert its antineoplastic effects after phosphorylation and direct incorporation into DNA and inhibition of DNA methyltransferase, causing hypomethylation of DNA and cellular differentiation or apoptosis. Decitabine inhibits DNA methylation in vitro, which is achieved at concentrations that do not cause major suppression of DNA synthesis. Decitabine-induced hypomethylation in neoplastic cells may restore normal function to genes that are critical for the control of cellular differentiation and proliferation. In rapidly dividing cells, the cytotoxicity of Decitabine may also be attributed to the formation of covalent adducts between DNA methyltransferase and Decitabine incorporated into DNA. Non-proliferating cells are relatively insensitive to Decitabine.
Decitabine is commercially supplied as a sterile lyophilized powder for injection, together with a buffering salt, such as potassium dihydrogen phosphate, and a pH modifier, such as sodium hydroxide. For example, decitabine is supplied as lyophilized powder packed in 20 mL glass vials, containing 50 mg of decitabine, monobasic potassium dihydrogen phosphate, and sodium hydroxide. As per the package insert leaflet of Dacogen®, it has to be aseptically reconstituted with 10 mL of Sterile Water for Injection (USP). Upon reconstitution, each mL contains approximately 5.0 mg of Decitabine at pH 6.7-7.3. Immediately after reconstitution, the solution has to be further diluted with 0.9% Sodium Chloride Injection, 5% Dextrose Injection, or Lactated Ringer's Injection to a final drug concentration of 0.1-1.0 mg/mL. Unless used within 15 minutes after reconstitution, the diluted solution must be prepared using cold (2° C.-8° C.) infusion fluids and stored at 2° C.-8° C. (36° F.-46° F.) for up to a maximum of 7 hours until administration. It is thus apparent that Decitabine is highly unstable in aqueous media.
Decitabine is most typically administered to patients by injection, such as by a bolus I.V. injection, continuous I.V. infusion, or I.V. infusion. The length of I.V. infusion is limited by the fast decomposition of Decitabine in aqueous media.
The disadvantage of lyophilized drugs is that they have to be reconstituted, usually by injecting a diluent through the septum into the vial. The drug is then drawn up into a new syringe, the needle has to be changed before the drug is finally being injected into the patient. These multiple steps are inconvenient and bear the risk of injuries from the exposed needles. This is especially disadvantageous for cytotoxic drugs such as Decitabine.
Decitabine is known to undergo degradation by oxidation and hydrolysis. U.S. Pat. No. 6,982,253 B2 discloses a liquid pharmaceutical composition comprising Decitabine solvated in a solvent that comprises glycerin, propylene glycol, polyethylene glycol, or combinations thereof, that comprises less than 40% water. The pharmaceutical composition further comprises additional excipients e.g. diluents, an acidifying agent and a cyclodextrin. Also, the Decitabine used in the preparation of the formulation has a defined particle size distribution, such that at least 50% of the particles have a particle size of below 10 micrometers. This is achieved by micronization. However, from the data provided in table 1, it is apparent that also the pharmaceutical compositions according to U.S. Pat. No. 6,982,253 are unstable. Moreover, the pharmaceutical compositions according to U.S. Pat. No. 6,982,253 require micronization of the drug due to its limited solubility in the described solvent systems as well as the higher viscosity of the latter.
Thus there still is a need for stable ready to use pharmaceutical compositions of Decitabine overcoming the disadvantages of the prior art.
It is thus an object of the present invention to provide ready to use, non aqueous pharmaceutical compositions comprising 5-aza-2′-deoxycitidine and at least one pharmaceutically acceptable aprotic solvent. The pharmaceutical compositions may further comprise at least one pharmaceutically acceptable protic solvent.
It is another object of the present invention to control the oxygen content by the addition of antioxidants or by using an inert gas such as nitrogen.
Another object of the present invention is to provide pharmaceutical compositions that are stable under both real time and accelerated storage conditions.
Yet another object of the present invention is to avoid the micronization of Decitabine.
Yet another object of the invention is to provide more cost efficient and economical formulations of decitabine.